If the shudder is continuous during that rpm span I would think you are looking at a lean condition.

If the shudder happens as you pass through that range during acceleration my guess would be a plug wire end. if its plain intermittant but only at that rpm, I would look to the throttle switch (check the 20 accel enrichment steps as the throttle is depressed KOEO key-on,engine-off).

Tell us more about the conditions existing when in failure - a freeze frame so to speak.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician